1. Field of the Invention
The present invention relates to an anchorage assembly for a pre-stressed concrete tendon, for use in past tensioning a pre-stressed concrete structure, and to a method of anchoring a tendon for use in post-tensioning the tendon in pre-stressed concrete.
2. Description of the Related Art
In the construction of pre-stressed concrete structures, anchorage assemblies are provided at opposite ends of a cables, commonly referred to as tendons, extending through the concrete structure. The anchorage assemblies comprise anchors which are embedded in the concrete and which are formed with bores for receiving the tendon ends. Wedges inserted into the anchor bores serve to retain the tendon ends relative to the anchors.
In U.S. Pat. No. 3,757,390, issued Sep. 11, 1973, to Hugh Jeremy Willis Edwards, there is described an anchorage assembly such as that described above, which is additionally provided with a sealing element of flexible material. The sealing element is inserted by means of a special tool into the bore and is formed with an external annular rib, which engages in and is retained by an annular recess formed in the bore. This sealing element serves to prevent the ingress of concrete into the bore of the anchor by filling the annular space between the periphery of the bore and the tendon. The sealing element comprises an annulus of flexible material having a bore which is preferably formed to conform to the outer periphery of the tendon and the annulus is split, or capable of being split, radially to facilitate positioning thereof over the tendon.
When this prior anchorage assembly is in use, the tendon is threaded through the bore of the anchor, which is attached to the shuttering. The sealing member is then clipped over the cable, and the special tool referred to above is employed to force the sealing member into the end of the anchor bore. Due to the relative tolerances of the bore and the outer diameter of the sealing member, and due to the compressibility of the sealing member, the sealing member is sufficiently compressed to be forced into the bore until its annular projection or rib becomes tightly engaged in the recess in the anchor bore.
It is a disadvantage of this prior arrangement that the special tool is required for this purpose. It is accordingly an object of the present invention to facilitate the provision of a seal between the anchor bore and the tendon without the use of a special tool and without the provision of an annular projection or rib for engagement in an annular recess in the bore.